This is mtemplate, a very simple text templating system. It has been
written for some small code generators (cfsm[1] in particular), but
you might find it useful too.
It is built on top of a simple generic type library for C (mobject),
loosely modelled on Python. The fundamental types supported are "None",
arrays, dictionaries (string-keyed lookups), strings and integers. Types
may be nested inside multi-valued types; e.g. arrays may contain other
arrays as an element, dictionaries may contain dictionaries of arrays,
etc. The library also supports iteration over arrays and dictionaries.
The template language is designed to be simple but useful. Template
directives are enclosed in double curly braces, e.g. "{{else}}".
Variable substitution is performed by placing the name of the variable in
curly braces, for example "{{users.djm.history[5]}}". mtemplate uses the
mobject namespace functions for variable substitutions - the syntax is
similar to that of Python or Javascript.
Comments are supported as "{{#this is a comment}}" and are ignored when
generating output.
Conditional statements are supported with the "{{if CONDITION}}", "{{else}}"
and "{{endif}}" directives. E.g.
{{if a.b}}text is a.b is true...
{{else}}more text if a.b is false...{{endif}}
The 'CONDITION' to an 'if' directive must be a valid namespace variable
reference, which is evaluated to a boolean using one of the following rules:
Integer variables True if integer is non-zero
String variables True if string is not empty
Array variables True if array has one or more elements
Dictionary variables True if dict has one or more elements
Loops are supported too, over libmobject arrays and dictionaries, using the
"{{for}}" and "{{endfor}}" keywords. For example:
{{for v in a.b}}
Key:{{v.key}}
Value:{{v.value}}
{{endfor}}
The loop variable ('v' in this example) is placed in the namespace with two
members, 'key' and 'value'. When iterating over a libmobject array, 'key' will
contain the array index (starting from zero), and 'value' will contain the
array element at that position. When iterating over a libmobject dictionary,
'key' will contain the dictionary key and 'value' the value referenced by that
key. Please note that dictionary iteration does not guarantee any particular
ordering.
The directive opening sequence itself can be inserted using the "{{{{}}"
escape sequence; any number of opening braces may be included in the escape
sequence. For example "{{{}}" => "{", "{{{{{{{}}" => "{{{{{", etc.
The "mtc" program can process mtemplate templates from the commandline.
It is mainly intended as a test/demo of mtemplate, but you might find it
useful. An example invocation:
mtc -Dusers.djm.name="Damien Miller" -Dusers.djm.uid=12345 \
-Dusers.djm.groups[0]=djm -Dusers.djm.groups[1]=users \
-o example.out example.x
To build mtemplate, just run "make". There are a bunch of regression
tests for mtemplate, mobject and some infrastructure bits; they may be
run through "make tests".
Damien Miller <djm@mindrot.org> 2007-04-06
[1] http://www.mindrot.org/projects/cfsm/
Damien Miller <djm@mindrot.org> 2007-03-27
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